
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21969.88    174.8362    22983.48    21627.19    22312.58
experime |  17,281    21678.36    171.3956    22531.19    21342.41    22014.31
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            291.5249     244.835               -188.3597    771.4094
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    diff = mean(control) - mean(experime)                         t =   1.1907
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8831         Pr(|T| > |t|) = 0.2338          Pr(T > t) = 0.1169
